If a > 0 and b > 0 and a + b = 1, then  is 

  1. ≥ 
  2. ≤ 
  3. ≥ 
  4. ≤ 

Answer (Detailed Solution Below)

Option 3 : ≥ 
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Detailed Solution

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 Concept:

  • Let x1, x2, ..., x∈ R then,
  1. The arithmetic mean of x1, x2, ..., xn is defined by   
  2. The geometric mean of x1, x2, ..., xn is defined by  
  3. The harmonic mean of x1, x2, ..., xn is defined by 

 

  • ​Arithmetic-Geometric mean inequality:   ≤ 


Calculations:

Given, a > 0 and b > 0 and a + b = 1, 

⇒  

⇒    

Now, a2 + b2 = (a + b)2 - 2ab

   (∵ a + b = 1 and   or   )

⇒ 

Now consider,

   | ∵  on squaring this we get  and so   

∴  

Hence, the correct answer is option 3)

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